363-206-295
Transmission and Synchronization Interfaces
5-24 Issue 1 December 1997
For DDM-2000 OC-3, function unit C, when equipped with an OC-3/IS-3 OLIU,
can be selected as an option for automatic synchronization reconfiguration. This
is useful in DRI networks where an OC-3 ring is connected through an OC-3/IS-3
optical interface to an OC-12 or FT-2000 OC-48 Lightwave System ring.
In OC-12 Release 5.1 and later ring releases, the sending of DS1 AIS on the
output of the BBF2B/BBF4 circuit pack can be provisioned by using the set-
sync command. Depending on the quality level of the incoming sync messages,
this new parameter can be provisioned to send DS1 AIS upon receiving level 5
(default), level 4, level 3, or level 2. Refer to Table 5-3 and Table 5-4 for definitions
of quality levels. AIS will be sent as long as the received message is at the
provisioned or greater in quality level number.
Examples 5
In this part, some detailed examples are given to show specifically how the
synchronization messages propagate through the DDM-2000 network and assist
in the recovery from a fiber failure. Through these examples, one can extend the
same concept to any other network that may include different topologies, number
of sites, failure locations, and number of BITS clocks.
NOTE:
All nodes in a ring using automatic synchronization reconfiguration must
have the synchronization messaging and automatic synchronization
reconfiguration features enabled to prevent alarms.
In all of the following examples, if the sync message parameter within the
set-oc3 or set-oc12 commands has been provisioned to “S byte” for an optical
interface, then the equivalent quality level S byte message will be transmitted from
that optical interface. The following are equivalent messages:
K2: Sync Quality Unknown is the same as, S1: Sync Trace Unknown
K2: Timing Looped Back is the same as, S1: Don’t Use
K2: Internal Clock is the same as, S1: Traceable SONET minimum Clock
K2: Stratum 3 is the same as, S1: Traceable Stratum 3.
Synchronization Reconfiguration Using an Externally Timed Access
Ring 5
Figure 5-9a shows an externally timed access ring operating in its normal
configuration. The DDM-2000 OC-3/OC-12 Multiplexer at the CO (Site A) is
externally timed from a BITS clock referenced to a PRS traceable source (host
node). The remaining DDM-2000 OC-3/OC-12 Multiplexers are externally timed
from a BITS clock referenced to a derived DS1.
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